Car Engine Sensors and their Symptoms of Failure

Car Engine Sensors and their Symptoms of Failure

Engine Sensors

Suzuki Liana Engine Sensors

Engine sensors on almost all modern cars work on the same principle. In this blog ‘Sensors functions’ and ‘Symptoms of failure’ will remain equally applicable to all car-makes, however, locations of sensors is mentioned for Suzuki Liana engine (M13a) in particular. Nonetheless, the sensor locations on other cars are also at similar locations / components as mentioned in this article.

Suzuki Liana is a modern age car with relatively more electronics-intense engine system as compared to cars of its category and era (2001-07). Suzuki Liana is equipped with new generation M-series engine with model numbers of M13a and M16a for 1.3L and 1.6L, respectively. Engine specifications make Suzuki Liana a highly fuel efficient and smoother car to drive.

I’ve come in contact with many people, who are unaware of the sensing mechanisms of Suzuki Liana, hence get carried away in the hands of car mechanics. I therefore decided to write this blog to give an overview to readers about Sensors installed on Suzuki Liana engine. I’ll try to cover the ‘function’, ‘location’ and ‘failure symptom’ of each sensor.

It is hoped that following information will be helpful for you. If you like it, your Registration with my website will be my appreciation OR at least hit the “LIKE” button below and share on your social network as a supportive gesture. Your feedback through comments will definitely help me in improving and presenting more blogs on Suzuki Liana.

Ok let’s discuss the Sensors one by one:-

Inlet Air Temperature Sensor (IAT)

Throttle Position Sensor (TPS)

Manifold Absolute Pressure Sensor (MAP)

Engine Coolant Temperature Sensor (ECT)

Crankshaft Position Sensor (CKP)

Lambda Sensor / Oxygen Sensor (O2 Sensor)


Inlet Air Temperature Sensor (IAT)

Function:

As the name shows, the function of IAT is to sense the temperature of air entering into the engine. This temperature signal is sent to engine Electronic Control Unit (ECU) which in turn corrects the fuel injection timing accordingly.  In winter season, IAT senses lower temperatures, hence, the ECU slightly increases the fuel injection time and keeps the engine RPMs relatively higher until engine is properly warmed up.

Location:

IAT is installed on Air Cleaner box. It is push fit and stays in place with the help of rubber pad.

Symptoms of Failure:

  • Engine Maintenance Light comes ON
  • Engine RPM low or high
  • RPM dips under load (e.g when initiating wheels roll)
  • Engine stalls etc

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Throttle Position Sensor (TPS)

Function:

TPS senses two parameters, the throttle (accelerator) pedal position  and the rate of pressing / releasing accelerator i.e how fast the accelerator has been pressed or released. In modern cars, this information is required by ECU for manipulating fuel injection timings for instantaneous response to variation of throttle position.

Location:

TPS is installed on throttle body with two screws.

Symptoms of Failure:

  • At times momentary flashing of engine maintenance light during accelerator movement for no apparent reason
  • Non-responsive accelerator
  • Power surges during constant speed drive
  • Engine misfire or RPM drop at a specific throttle (accelerator) position during acceleration or deceleration
  • Momentary dip in RPM during idling

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Manifold Absolute Pressure Sensor (MAP)

Function:

There are two different sensors used in modern vehicles for measuring amount of air entering the engine, one is MAP (Manifold Absolute Pressure) sensor and the other is MAF (Mass Air Flow) sensor. Though the purpose of both sensor is same but their working principles are entirely different and can not be used interchangeably. MAP senses the pressure while the MAF senses the Mass flow rate.

Suzuki Liana is installed with MAP sensor. MAP sensor is used to measure the amount of air entering into the engine for making mixture with fuel for combustion. MAP sensor senses the absolute air pressure in the inlet duct (big black pipe directing air from air cleaner to throttle body and then to the inlet manifold), and sends this information to Electronic Control Unit (ECU) in the form of electrical signal. ECU, which is also getting inlet air temperature information through IAT sensor, calculates the air mass flow (amount of air) on the basis of these two information. Once the amount of air is known, the ECU gives signal to injectors for providing correct amount of fuel in order to have best air-fuel mixture for optimum combustion. On the basis of MAP and  IAT information, the ECU keeps correcting the fuel injection timing to keep the drive most fuel efficient.

Location:

MAP is installed on throttle body, downstream (after) of the throttle body butterfly. MAP sensor is installed with two Allen-key screws.

Symptoms of Failure:

  • Low mileage per liter due to inaccurate fuel injection timing
  • Engine throttle at times become non-responsive due to fuel overflow condition (rich mixture)
  • Smell of un-burnt fuel from engine exhaust gases
  • Engine misfire due to lean mixture
  • Rough idle RPM
  • Engine knocking under load condition
  • Hesitation during acceleration or at beginning of wheels roll

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Engine Coolant Temperature Sensor (ECT)

Function:

Engine Coolant Temperature (ECT) sensor is generally known as water temperature sensor and is considered the most important sensor and is often considered as a “Master” sensor. As we all know that coolant (water) circulates around the engine to keep it cool against the heat effects caused by combustion in engine cylinders. Like all other sensors it also generates an electrical signal as soon as the coolant temperature varies. This electrical signal from Coolant Temperature sensor does three functions:-

  1. Shows temperature indication for the driver.
  2. Electrical signal goes to ECU for adjustment of fuel. At low coolant temperatures, RPM remains higher than normal till the time engine reaches at normal operating temperatures.
  3. Gives signal to Radiator fan for automatic ON / OFF as per the requirement.

Location:

ECT is installed on a metallic housing installed on the left-side of the engine (when viewing forward from inside) . At this location, water is coming out of the engine after absorbing engine heat which is sensed by ECT sensor and requisite functions are performed. ECT is threaded on to the metallic housing.

Symptoms of Failure:

  • Faulty ECT will show inaccurate temperature on the gauge.
  • Failed ECT will indicate lower (or minimum) temperature on gauge.
  • High engine idle RPMs.
  • Smell of un-burnt fuel from engine exhaust gases due to excessive fuel supply by ECU which senses engine as cold whereas physically engine is warm.
  • Engine heats up due to inoperative radiator fan (sensing engine as cold).
  • Engine knocking due to over-temp condition.

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Crankshaft Position Sensor (CKP)

Function:

In older cars crankshaft rotation (generally known as engine timing) was manually adjusted with the help of distributors, whereas now in modern cars installed with electronic control units, the function of distributor is now being performed by Crankshaft Position Sensor (CKP). As the name shows, the Crankshaft position sensor senses the rotational speed of crankshaft and sends and electrical signal to ECU, which in response, adjusts the ‘spark-firing’ and ‘fuel injection’ timings to get optimal performance of engine, especially during starting cycle.

Location:

CKP is installed on the engine block in the surroundings of timing chain mechanism so that movement of crankshaft is sensed. CKP is threaded to the engine block housing.

Symptoms of Failure:

  • Problematic starting or delayed ignition
  • Unstable Idle RPM with engine shaking
  • Unexpected engine stalls
  • Unable to maintain constant speed during highway drive
  • Hesitation to accelerate or Jerky acceleration
  • At higher accelerator settings, Engine misfiring, backfiring or high vibrations
  • Unable to start when engine is hot, however starts when engine is cooled down after some time

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Lambda Sensor / Oxygen Sensor (O2 Sensor)

Function:

There are three names of the same sensor which are used interchangeably, but generally known as O2 Sensor. The function of this sensor is to sense the concentration of oxygen contents in the exhaust gases. If the O2 concentration is high that means engine is running on lean mixture (means more air contents) and if the O2 contents are low then the mixture is considered rich. This sensor generates an electrical signal and sends it to the ECU which adjusts the fuel injection timings and also opens the Exhaust Gas Regulator (EGR) for recycling of exhaust gases back into the intake manifold. Hence, O2 sensor ensures optimal fuel consumption by the engine. Automobiles installed with Catalytic Converter (CAT), there are TWO Lambda sensors installed, one just after the Exhaust manifold at the beginning of exhaust pipe while the other one after the CAT. First O2 sensor analyses the combustion efficiency of engine while the other one analyses the effectivity of Catalytic Converter. ECU utilizes signals of both sensors for fuel correction in order to give optimal fuel efficiency.

Location:

For automobiles with CAT, two O2 sensors are installed, one before the CAT and other one after the CAT. Whereas, only one O2 sensor is installed on automobiles without CAT which is located  at the beginning of exhaust pipe (silencer).

Symptoms of Failure:

  • High fuel consumption
  • Smell (usually like rotten egg) from exhaust gases when engine is cold
  • Unstable Idle RPM or Unexpected engine stalls
  • Unable to maintain constant speed during highway drive
  • Hesitation to accelerate

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